The processing of waste including municipal waste, medical waste, toxic and radioactive waste by means of plasma-torch based waste processing plants is well known.
One problem commonly encountered in the operation of such plants is that of minimizing the production and emission of chlorine containing compounds resulting from the plasma treatment of the waste. Waste, particularly municipal solid waste (MSW), typically comprises a mixture of solid waste which often contains unpredictable levels of chlorine containing materials, for example, PVC pipes, plastic containers, etc. If too large an amount of such materials is processed at any one time in the processing plant, then the level of emission of pollutants containing chlorine may exceed safety and/or legal limits, requiring the plant to be shut down temporarily or alternatively upgrading the gas cleaning system, thus increasing the cost of operation and/or investment of the plant. Further, high levels of chlorine-containing materials may also cause harm to the equipment of the plant, requiring more frequent maintenance operations and may also interfere with the chemical processes that take place during the processing procedure.
Accordingly, it would be advantageous in such plants to monitor the composition of the waste before it is fed into the plant, and to remove from processing, at least temporarily, batches of waste having excessively high chlorine content.
U.S. Pat. No. 3,794,843 relates to a gauge for determining the percentage by weight of moisture contained in a bulk material. U.S. Pat. No. 4,028,267 is directed to an apparatus and method for measuring the concentration of iron in iron ore, by exposing the material to a neutron source. JP 10258428, JP 2002137224, JP 2000126649 and JP 06210632 describe various means for separating or sorting plastics from other material, none of which means makes use of a neutron generator. U.S. Pat. No. 4,702,379 and U.S. Pat. No. 4,830,193, relate to a plant specifically for sorting discrete pieces of gold ore which is irradiated while descending through rotating cylinders in a continuous process.
However, none of these references provides a solution to or in fact even addresses the problems relating to determining the content of chorine-containing materials in waste, particularly for the purpose of removing such waste from subsequent processing in a plasma-torch based processing plant if the amount of chlorine exceeds a predetermined value.
It is therefore an aim of the present invention to provide an apparatus for determining the level of chlorine-containing materials in batches of waste prior to feeding them into a plasma waste converting plant, and a system for separating and processing waste that contains a quantity of chorine-containing material that exceeds a predetermined threshold value.
It is another aim of the present invention to provide such an apparatus and system that may be incorporated into a municipal solid waste processing apparatus.
It is another aim of the present invention to provide such an apparatus and system that is relatively simple mechanically and thus economic to incorporate into a processing plant design.
It is another aim of the present invention to provide such an apparatus and system that is incorporated as an integral part of a plasma-torch based type waste converter.
It is also an aim of the present invention to provide such an apparatus and system that is readily retrofittable with respect to at least some existing plasma-torch based waste converters and other systems for thermal treatment of waste such as incinerators.
Further purposes and advantages of this invention will appear as the description proceeds.